The invention relates to iodine gas lasers. Oxygen-iodine transfer lasers are utilized in Government research programs pertaining to high energy lasers. A measured amount of I.sub.2 vapor must be supplied to the oxygen-iodine transfer laser in order to produce lasing. Precise control of the oxygen-iodine laser requires that an adjustable and reproducible amount of I.sub.2 be introduced into a carrier gas flowing to the laser, without any appreciable effect on the carrier gas flow rate.
Iodine lasers have in the past been supplied with iodine vapor by placing iodine crystals in an evacuated container. The iodine crystals at ambient temperatures or higher will sublime generating an I.sub.2 vapor in the container. A carrier gas is passed through the container of iodine crystals where it mixes with the I.sub.2 vapor prior to being supplied to the laser. In the past the density of the iodine vapor in the container, and thus the amount of I.sub.2 added to a carrier gas flow, has been controlled by heating the container of I.sub.2 crystals or by heating the I.sub.2 crystals with an electrical resistance heater. This method of supplying the heat of sublimation, or vaporization, to the solid iodine has the disadvantage of there being no way of quickly changing the rate at which the I.sub.2 crystals sublime.